Function canon_fn_signature 

pub fn canon_fn_signature(
    f: &FnSignature,
    types: &HashMap<String, Arc<TypeDecl>>,
) -> String

P8.1 (#1512, [DECISION C]): the canonical form of a FnSignature — extends this module’s own canon_type (ADR 0200) to a shape it doesn’t reach today. Body-free by construction ([DECISION B]): there is no body/requires/ensures field on FnSignature to accidentally include here.